this is a basic master muffin recipe that is fairly plain, so we recommend adding other flavorings or fruit . this recipe can easily be halved and doubled, if desired. if doubling the recipe, mix the batter in a large bowl and take care to evenly incorporate the flavorings. we prefer whole milk yogurt, although the recipe will work with low-fat or nonfat. when storing the batter overnight in the refrigerator, you can either put it in an airtight container or, if you have space, in a muffin tin covered with greased plastic wrap. you can substitute frozen blueberries for the fresh; they must be thawed, rinsed, and dried, but they do not need to be tossed with flour.